414 CONSIDERATION OF CARBON COMPOUNDS. 



Fibrinogen may be obtained by allowing blood to run directly 

 from the vessels into a weak solution of magnesium sulphate, then 

 separating the corpuscles, and precipitating the fibrinogen by satu- 

 rating the solution with sodium chloride. The precipitate is collected 

 on a filter and purified by dissolving it in an 8 per cent, solution of 

 sodium chloride, and reprecipitating it by again saturating the solu- 

 tion with the salt. 



c. Myosin. Living muscular tissue contains a yellowish, opalescent 

 fluid (muscle-plasma), which filters with difficulty and clots at tem- 

 peratures above C. (32 F.J. This clotting or coagulation of 

 muscle-plasma also takes place after death and gives rise to the con- 

 dition known as rigor mortis. This change is similar to the forma- 

 tion of fibrin in the blood and possibly due to the action of a myosin 

 ferment. 



Myosin is obtained by extracting muscular tissue with 10 per cent, 

 solution of ammonium chloride (in which it is readily soluble) and 

 precipitating it from this solution by the addition of large quantities 

 of water. 



Aside from the general reactions characteristic of globulins it is 

 distinguished by the low temperature of 40 to 50 C. (104 to 122 

 F.), at which it coagulates when dissolved in salt solutions. 



d. Orystallin and Vitellin are globulins which resemble one another 

 so closely that they may be identical. Crystallin occurs in crystalline 

 lenses to the extent of nearly 25 per cent. ; vitellin is found in the 

 yolk of hens' eggs to the amount of about 15 per cent. Both sub- 

 stances are white, flaky solids, readily soluble in dilute acids and 

 alkalies, and also in a 10 per cent, solution of sodium chloride. The 

 latter solution is coagulated by heating to 75 C. (167 F.). 



Class III. Derived albumins or albuminates. These sub- 

 stances are insoluble in water, and in dilute neutral salt solutions ; 

 soluble in dilute acids and alkalies. Solution not coagulated on 

 heating. 



a. Acid-albumins. When the solution of a native albumin, such 

 as serum- or egg albumin, is treated for some little time with a dilute 

 acid (hydrochloric acid) its properties become entirely changed. Thus : 

 the solution is no longer coagulated by heat, and on neutralizing it 

 carefully the whole of the albumin is precipitated. This shows that 

 the native albumin, which is soluble in water and in neutral salt 

 solutions, has been changed into a form insoluble in these agents, and 

 this modified form is termed acid-albumin. Acid-albumins, while 



